Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features and advantages of the enclosed embodiments will be apparent from the following description.
Third generation Partnership Project (3GPP) fifth generation (5G) systems (e.g., new radio (NR)), may use one or more mapping types for uplink and downlink radio transmissions. An example of mapping type information is information indicating whether physical downlink shared channel (PDSCH) is mapping type A or mapping type B.
While certain embodiments are described with respect to PDSCH mapping types A and B, particular embodiments may apply to other mapping type information and other mapping types, such as mapping types for uplink communication, such as physical uplink shared channel (PUSCH).
Downlink data transmission in NR may start at the beginning of a slot or may start at a later position within the slot. Similarly, the data transmission may end before the end of the slot. This is sometimes referred to (not necessarily in a very carefild manner) as “slot-based” and “mini-slot” or “non-slot-based” transmission, respectively. NR specifications include two different PDSCH mapping types, type A and type B. The difference between the two is the placement of the downlink demodulation reference signal (DM-RS).
In mapping type A, the DM-RS is placed at the beginning of the slot, either at the third or fourth orthogonal frequency division multiplexing (OFDM) symbol (signaled on the physical broadcast channel (PBCH)). In mapping type B, the DM-RS is placed at the beginning of the transmitted data. Thus, mapping type A is suitable for slot-based transmission and mapping type B may be used for non-slot-based transmission (although it in principle can be used for any transmission length).
A user equipment (UE) needs to know whether PDSCH mapping type A or B is used for a particular transmission. Current NR specifications and agreements do not specify how to indicate to the UE whether PDSCH mapping type A or B is used.
One possibility is semi-static configuration of the mapping type. For this to work, a default mapping type is defined and used for the initial configuration signaling form the network. Given NR agreements that system information can be transmitted using mini-slots, type B has to be the default.
Another possibility is to indicate in the downlink control information (DCI) the mapping type used. This approach may provide a large amount of flexibility at the cost of one DCI bit. As stated above, downlink data transmissions have some flexibility in the starting position in a slot, as well as the number of OFDM symbols used for the transmission. It has been agreed to signal the start and length through a table (i.e., the DCI contains an index which selects one of a plurality of entries in a (configurable) table). As an example, 3 bits may be used for the index giving 8 different possibilities of starting position/length for downlink data transmission.
Some proposals may include multiple time allocation tables, for example, one for slot-based transmission and one for non-slot-based transmission. In these proposals, the bit indicating PDSCH mapping type A or B may be used to select the time allocation table to use.